JP5330728B2 - Brushless motor drive device - Google Patents

Description

  The present invention relates to a brushless motor drive device, and more particularly to a sensorless drive system suitable for sensorless detection of the rotor position of a brushless motor comprising a rotor having a permanent magnet and a stator having a multi-phase stator coil. The present invention relates to a brushless motor driving apparatus.

2. Description of the Related Art Conventionally, a brushless motor driving device that detects a rotor position by using an induced voltage generated in a stator coil of each phase is known (see, for example, Patent Document 1). In this drive device, the terminal voltage of each stator coil is detected and compared with a reference voltage. Then, a phase signal indicating that the rotor has reached a specific position is output at the timing when the detected terminal voltage intersects the reference voltage, and energization to the stator coil for driving the motor is controlled. For this reason, according to such a drive device, without providing a dedicated sensor for detecting the rotor position, the rotor position is detected using the induced voltage generated in the stator coil of each phase, and the drive control of the brushless motor is performed. Can be executed.
Japanese Patent No. 3308680

  By the way, external noise and ringing noise may occur. If these noises are superimposed on the induced voltage of the stator coil, the normal induced voltage is detected even though it does not reach the reference voltage. Therefore, the phase signal may be erroneously output by crossing the reference voltage, so that accurate rotor position detection is not performed and drive control of the motor is not appropriately performed.

  In the driving device described in Patent Document 1, the falling edge of the pulse width modulation signal for controlling the energization to the stator coil of each phase is used as the induced voltage detection determination timing, and the voltage detected at that timing is determined. Compared with the reference voltage, the phase signal is output. However, even in such a device, when noise is superimposed at the above-described determination timing, the detected voltage crosses the reference voltage and a phase signal is erroneously output. Further, in such an apparatus, since it is necessary to detect the falling edge of the pulse width modulation signal in order to generate the determination timing, if the pulse width modulation signal is a signal with a duty of 100%, the falling edge is originally It is not detected, and the above determination timing itself cannot be generated. As a result, there may occur a situation in which the phase signal cannot be output even though the induced voltage crosses the reference voltage.

  The present invention has been made in view of the above points, and a noise brushless motor capable of detecting the rotor position regardless of the state of the pulse width modulation signal and suppressing the influence of noise for detecting the rotor position. An object of the present invention is to provide a driving apparatus.

The above-described object is a brushless motor driving device including a rotor position specifying unit that specifies a rotor position based on an induced voltage generated in each phase of a stator coil, and detects a terminal voltage of each phase of a stator coil. As comparison results of detection means, comparison means for comparing the terminal voltage detected by the terminal voltage detection means with a reference voltage that serves as a reference in specifying the rotor position by the rotor position specifying means, and comparison results of the comparison means when the terminal voltage is determined to state the at reference voltage above or below and a time determining means for determining whether or not to continue a predetermined time, the state by the time determination means has continued the predetermined time, before Symbol and the induced voltage detecting means for induced voltage is detected to be intersected with the reference voltage, the predetermined time, controls the power supply to each phase of the stator coils Is achieved by a drive device for a brushless motor comprising a first determination time changing means duty ratio or duty cycle of the pulse width modulation signal is increased in response to the increase, the for.
Another object of the present invention is to provide a brushless motor driving device including a rotor position specifying unit that specifies a rotor position based on an induced voltage generated in each phase of the stator coil, and detects a terminal voltage of each phase of the stator coil. Comparison of the terminal voltage detection means, the comparison means for comparing the terminal voltage detected by the terminal voltage detection means with a reference voltage that is a reference for specifying the rotor position by the rotor position specifying means, and the comparison means As a result, when it is determined by the time determination means whether the state in which the terminal voltage is equal to or higher than the reference voltage continues for a predetermined time, and the time determination means determines that the state has continued for the predetermined time, Inductive voltage detection means for detecting that the induced voltage crosses the reference voltage, and the predetermined time, the energization of the stator coils of each phase is performed. A first determination time changing means for setting the duty on time or shorter than the duty cycle according to the duty ratio or duty cycle of the pulse width modulation signal for Gosuru is achieved by a drive device for a brushless motor comprising a.
Another object of the present invention is to provide a brushless motor driving device including a rotor position specifying unit that specifies a rotor position based on an induced voltage generated in each phase of the stator coil, and detects a terminal voltage of each phase of the stator coil. Comparison of the terminal voltage detection means, the comparison means for comparing the terminal voltage detected by the terminal voltage detection means with a reference voltage that is a reference for specifying the rotor position by the rotor position specifying means, and the comparison means As a result, when it is determined by the time determination means whether the state in which the terminal voltage is equal to or higher than the reference voltage continues for a predetermined time, and the time determination means determines that the state has continued for the predetermined time , response and the induced voltage detecting means for detecting that the pre-Symbol induced voltage crosses the reference voltage, the predetermined time, for the reference voltage increases A second determination time changing means for long Te is achieved by a drive device for a brushless motor comprising a.

  In the invention of this aspect, the terminal voltage of the stator coil of each phase is detected and compared with the reference voltage. Then, when the detected terminal voltage is equal to or higher than the reference voltage for a predetermined time, the neutral point of the induced voltage that is a reference for specifying the rotor position is detected, and the rotor position is specified. . In such a configuration, the rotor position can be detected even if the pulse width modulation signal for controlling the energization of the stator coils of each phase is a signal with a duty of 100%. In addition, since it is possible to distinguish between the normal induced voltage and the short-time noise superimposed on the induced voltage, the influence of noise on the rotor position detection is suppressed.

In the brushless motor driving apparatus described above, a first determination time change in which the predetermined time is changed according to a duty ratio or a duty cycle of a pulse width modulation signal for controlling energization to the stator coils of each phase. By providing the means, it is possible to improve the accuracy of distinguishing between the normal induced voltage and the short-time noise.
At this time, the first determination time changing means further the predetermined time may be longer depending on the prior SL reference voltage increases.

  Further, in the brushless motor driving apparatus described above, if the second determination time changing means for changing the predetermined time according to the reference voltage is provided, a normal induced voltage is distinguished from short-time noise. Accuracy can be improved.

  By the way, in the brushless motor driving apparatus described above, if it is provided with energization control means for controlling the timing of energizing the stator coils of each phase based on the rotor position specified by the rotor position specifying means, The drive control of the motor based on this can be performed appropriately.

  According to the present invention, it is possible to detect the rotor position regardless of the state of the pulse width modulation signal for controlling the energization to the stator coil of each phase, and to suppress the influence of noise in performing the rotor position detection. be able to.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an overall configuration diagram of a drive device 12 for a brushless motor 10 according to an embodiment of the present invention.

  In this embodiment, the brushless motor 10 includes a rotor (not shown) having permanent magnets and a stator 14 having three-phase U, V, W stator coils 14U, 14V, 14W. One end of each of the stator coils 14U, 14V, and 14W is connected in common, and the other end is connected to the output terminals 17U, 17V, and 17W of the inverter circuit 16 included in the drive device 12.

  The inverter circuit 16 is configured by connecting six switch elements 20a, 20b, 22a, 22b, 24a, and 24b between the positive terminal and the negative terminal of the DC power supply 18 in a three-phase bridge. Each switch element 20 to 24 is, for example, an n-channel MOS transistor. A free wheel diode 26 is connected to each of the switch elements 20 to 24. The common connection point between the switch elements 20a and 20b is the output terminal 17U, the common connection point between the switch elements 22a and 22b is the output terminal 17V, and the common connection point between the switch elements 24a and 24b is the above-described output terminal 17V. Output terminal 17W. Each of the switch elements 20 to 24 is turned on / off in accordance with an instruction from the main control circuit 48 provided in the driving device 12.

  The non-inverting input terminals of the comparators 30U, 30V, and 30W are connected to the output terminals 17U, 17V, and 17W. The inverting input terminals of the comparators 30U, 30V, and 30W are connected to the reference voltage terminal 32. The reference voltage terminal 32 is a common connection point of voltage dividing resistors 34 and 36 provided in series between the positive terminal and the negative terminal of the DC power supply 18. The comparators 30U, 30V, and 30W compare the terminal voltages VU, VV, and VW generated at the output terminals 17U, 17V, and 17W with the reference voltage of the reference voltage terminal 32. A low signal is output when the terminal voltages VU, VV, and VW are less than the reference voltage, and a high signal is output when the terminal voltages VU, VV, and VW are equal to or higher than the reference voltage.

  The drive device 12 has a control device 40 mainly composed of a microcomputer. The control device 40 is a device that controls the driving of the brushless motor 10 and performs pulse width modulation (PWM) control to adjust the output based on the rotation speed instruction signal of the motor 10. The control device 40 includes a selection circuit 42, a counter 44, a comparison circuit 46, a main control circuit 48, a voltage value monitoring circuit 50, a determination time generation circuit 52, and a PWW signal generation circuit 54.

  The output terminals of the comparators 30U, 30V, 30W are connected to the input terminal of the selection circuit 42. The outputs of the comparators 30U, 30V, and 30W are supplied to the selection circuit 42. The selection circuit 42 is also connected to the main control circuit 48, specifies the phase to be monitored according to the instruction from the main control circuit 48, and selects the outputs of the comparators 30U, 30V, 30W corresponding to the phase.

  The output terminal of the selection circuit 42 is connected to the input terminal of the counter 44. The output of the selection circuit 42 is supplied to the counter 44. The counter 44 measures the high time Tc when the output of the comparators 30U, 30V, 30W selected by the selection circuit 42 is a high signal, while the low time Tc is measured when the output is a low signal. taking measurement. The output terminal of the counter 44 is connected to the input terminal of the comparison circuit 46. The output of the counter 44 is supplied to the comparison circuit 46. The comparison circuit 46 is also connected to the determination time generation circuit 52 and compares the high time or the low time Tc supplied from the counter 44 with a later-described determination time Tp supplied from the determination time generation circuit 52.

  A signal (PWM_Duty instruction signal) indicating a PWM duty ratio is supplied to the input terminal of the PWM signal generation circuit 54 so that the difference between the rotation speed instruction signal of the brushless motor 10 and the actual rotation speed detection signal is zero. Is done. The PWM signal generation circuit 54 generates a PWM signal having the instructed duty ratio based on the supplied PWM_Duty instruction signal.

  Both the output terminal of the comparison circuit 46 and the output terminal of the PWM signal generation circuit 54 are connected to the input terminal of the main control circuit 48. Both the output of the comparison circuit 46 and the output of the PWM signal generation circuit 54 are supplied to the main control circuit 48. The main control circuit 48 has six output ports connected to the input terminals (gate terminals) of the six switch elements 20 to 24 described above.

  The main control circuit 48 detects the position of the rotor based on the output from the comparison circuit 46, and calculates the energization timing to the stator coils 14U, 14V, 14W. The gate signal to be supplied to the switch elements 20 to 24 of the inverter circuit 16 when the stator coils 14U, 14V, and 14W are energized is modulated by the PWM signal from the PWM signal generation circuit 54, and each switch is output from the output port. Supply to elements 20-24. Further, the main control circuit 48 specifies a phase (specifically, a non-energized phase) to be monitored for rotor position detection based on the detected rotor position, and supplies the information to the selection circuit 42. .

  An input terminal of the voltage value monitoring circuit 50 is connected to the reference voltage terminal 32 that is a common connection point between the resistor 34 and the resistor 36. The voltage value monitoring circuit 50 is a circuit that monitors a power supply voltage (specifically, a reference voltage divided by the resistor 34 and the resistor 36) generated in the DC power supply 18. Note that the reference voltage at the reference voltage terminal 32 is set to a voltage (neutral point) approximately halfway between the power supply voltage of the DC power supply 18 and the ground voltage.

  Both the output terminal of the PWM signal generation circuit 54 and the output terminal of the voltage value monitoring circuit 50 are connected to the input terminal of the determination time generation circuit 52. Both the output of the PWM signal generation circuit 54 and the output of the voltage value monitoring circuit 50 are supplied to the determination time generation circuit 52. The determination time generation circuit 52 calculates the determination time Tp to be supplied to the comparison circuit 46 based on the output from the PWM signal generation circuit 54 and the output from the voltage value monitoring circuit 50, as will be described in detail later. Information is supplied to the comparison circuit 46.

  Next, the operation of the driving device 12 of the brushless motor 10 of this embodiment will be described with reference to FIG. FIG. 2 shows an operation time chart for detecting the rotor position in the driving device 12 of the brushless motor 10 of this embodiment.

  In the present embodiment, the control device 40 controls the inputs (gate signals) to be supplied to the switch elements 20 to 24 of the inverter circuit 16, whereby each of the U-phase, V-phase, and W-phase stators of the brushless motor 10. The energization of the coils 14U, 14V, and 14W is controlled to control the rotational drive of the brushless motor 10.

  When energization of the stator coils 14U, 14V, and 14W is controlled, an induced voltage is generated in the stator coils 14U, 14V, and 14W. The energization control for each of the stator coils 14U, 14V, and 14W is realized by alternately performing 120 ° energization and 60 ° non-energization, and is performed while being shifted by 120 ° between the phases. When such energization control is performed, an induced voltage is generated in the non-energized phase.

  For example, when the energization state of the stator coils 14U, 14V, and 14W is switched from energization to non-energization, a pulsed back electromotive force is generated in the stator coils 14U, 14V, and 14W in the positive or negative direction with reference to the reference voltage. Then, an induced voltage is induced and the induced voltage increases. This induced voltage is output as terminal voltages VU, VV, VW of the output terminals 17U, 17V, 17W connected to the stator coils 14U, 14V, 14W. When the non-energization continues for 60 °, the energized state is switched from non-energized to energized. After such switching, a positive or negative constant voltage based on the reference voltage appears at the output terminals 17U, 17V, and 17W until the energized state is switched from energized to non-energized. When energization continues for 120 °, the energized state is switched from energized to non-energized, and pulsed counter electromotive force is generated in the stator coils 14U, 14V, and 14W in the negative or positive direction with reference to the reference voltage.

  The control device 40 detects the rotor position using the induced voltage appearing at the output terminals 17U, 17V, and 17W of each phase (non-energized phase). That is, the terminal voltages VU, VV, VW of the output terminals 17U, 17V, 17W connected to the stator coils 14U, 14V, 14W are input to the non-inverting input terminals of the comparators 30U, 30V, 30W. Further, the inverting input terminals of the comparators 30U, 30V, and 30W are connected to the reference voltage terminal 32 divided by the voltage dividing resistors 34 and 36 provided in series between the positive terminal and the negative terminal of the DC power supply 18. A voltage is input.

  The comparators 30U, 30V, and 30W compare the terminal voltages VU, VV, and VW with a reference voltage, detect a cross point between them, and output a high or low phase signal. The main control circuit 48 specifies the rotor position based on the timing at which the phase signal is supplied from the comparators 30U, 30V, 30W corresponding to the non-energized phase, and generates a pulsed position signal. Then, a time (30 °) for switching between the energized phase and the non-energized phase is calculated from the switching timing of the position signal between high and low, and the energized state is switched at the timing when that time is reached.

  The main control circuit 48 sequentially turns on and off the six switch elements 20 to 24 of the inverter circuit 16 according to the switching timing of the energized state calculated as described above, and energizes the stator coils 14U, 14V, and 14W, and The brushless motor 10 is driven to rotate.

  By the way, in the present embodiment, the control device 40 performs PWM control so as to adjust the output so that the difference between the rotational speed instruction signal of the brushless motor 10 and the actual rotational speed detection signal becomes zero. Therefore, since the gate signals supplied to the switch elements 20 to 24 of the inverter circuit 16 are PWM-modulated, the terminal voltages VU, VV, VW of the output terminals 17U, 17V, 17W become pulse voltages, and the comparators 30U, 30U, The phase signal that is the output of 30V and 30W also has a pulse shape.

  On the other hand, external noise and ringing noise are superimposed on the terminal voltages VU, VV, VW of the non-energized phase output terminals 17U, 17V, 17W in addition to the normal induced voltages induced in the stator coils 14U, 14V, 14W. Sometimes. In this case, even though the normal induced voltage does not reach the reference voltage, the terminal voltages VU, VV, and VW cross the reference voltage and a phase signal is erroneously output, so that accurate rotor position detection is performed. Is not performed, and the drive control of the brushless motor 10 is not appropriately performed.

  The falling edge of the PWM signal from the PWM signal generation circuit 54 is used as the induced voltage detection determination timing, and the terminal voltage VU, VV, VW detected at that timing is compared with the reference voltage to perform the phase signal output processing. It is possible to do it. However, even in this configuration, the terminal voltage VU, VV, VW detected due to the above-described noise or the like crosses the reference voltage, and a phase signal is erroneously output. Further, in such a device, since it is necessary to detect the falling edge of the PWM signal in order to generate the determination timing, if the PWM signal is a signal having a duty of 100%, the falling edge is not detected in the first place. The determination timing itself cannot be generated, and as a result, a situation may occur in which the phase signal cannot be output even though the normal induced voltage crosses the reference voltage.

  Therefore, the driving device 12 of the brushless motor 10 of the present embodiment prevents such a situation and appropriately detects the rotor position. Hereafter, the characteristic part of a present Example is demonstrated with reference to FIG. 3 thru | or FIG.

  FIG. 3 shows a characteristic operation time chart in the driving device 12 of the brushless motor 10 of this embodiment. FIG. 4 shows a flowchart of an example of a control routine executed in the driving device 12 of the brushless motor 10 of the present embodiment. FIG. 5 shows a map used to calculate the determination time Tp in the driving device 12 of the brushless motor 10 of the present embodiment.

  In the drive device 12 of the present embodiment, the control device 40 measures the duty-on time of the PWM signal based on the PWM signal supplied from the PWM signal generation circuit 54 in the determination time generation circuit 52 (step 100). And / or the power supply voltage of the DC power supply 18 is detected based on the reference voltage supplied from the voltage value monitoring circuit 50 (step 102). Then, a determination time Tp to be used in the comparison circuit 46 is calculated and generated based on the duty on time and / or the power supply voltage value (step 104).

  Specifically, the determination time generation circuit 52 sets, for example, 90% shorter than the current duty-on time of the PWM signal as the determination time Tp (FIG. 5A), and also according to the power supply voltage value. Specifically, the longer the power supply voltage value, the longer the determination time Tp (for example, 10 μs when the voltage value is 16 volts, 8 μs when the voltage value is 12 volts, and 6 μs when the voltage value is 8 volts) is calculated (FIG. 5 (B)). For example, a time of 50% shorter than the current duty on time of the PWM signal (however, a time shorter than the case where the determination time Tp is set by the duty on time alone) and a time corresponding to the power supply voltage value (however, , A time shorter than the case where the determination time Tp is set solely by the power supply voltage value; for example, 5 μs when the voltage value is 16 volts, 4 μs when the voltage value is 12 volts, and 3 μs when the voltage value is 8 volts) May be set as the determination time Tp.

  Further, in the counter 44 corresponding to the non-energized phase, the control device 40 uses the terminal voltages VU, VV, VW of the output terminals 17U, 17V, 17W when the outputs of the comparators 30U, 30V, 30W are high signals or low signals. Is equal to or higher than the reference voltage, the high time or the low time Tc during which the terminal voltage VU, VV, VW is in the high state where the terminal voltage is higher than the reference voltage or the low state where the terminal voltage is lower than the reference voltage continues is measured (step 106). .

  Information on the determination time Tp calculated and set by the determination time generation circuit 52 and information on the high time or low time Tc measured by the counter 44 are supplied to the comparison circuit 46. In the comparison circuit 46, the control device 40 compares the high time or low time Tc from the counter 44 with the determination time Tp from the determination time generation circuit 52, and determines whether or not the high time or low time Tc is equal to or greater than the determination time Tp. Is determined (step 108).

  When the comparison circuit 46 determines that the high time or the low time Tc is equal to or greater than the determination time Tp, the comparison circuit 46 detects the cross points of the terminal voltages VU, VV, VW and the reference voltage, and outputs the high phase signal as the main signal. Output to the control circuit 48. The control device 40 detects in the main control circuit 48 that the induced voltage induced in the stator coils 14U, 14V, 14W crosses the reference voltage based on the timing when the high phase signal is supplied from the comparison circuit 46. Then, the rotor position is specified (step 110). Then, switching between the energized phase and the non-energized phase is performed at a timing when a time corresponding to an electrical angle of 30 ° has elapsed from the specified rotor position.

  On the other hand, when the comparison circuit 46 determines that the high time or the low time Tc is less than the determination time Tp, the comparison circuit 46 outputs a low phase signal to the main control circuit 48. When the low phase signal is supplied in the main control circuit 48, the control device 40 determines that there is a possibility that noise or the like is superimposed on the terminal voltages VU, VV, VW (step 112).

  Thus, in the driving device 12 of the present embodiment, the high time or the low time Tc in which the high state in which the terminal voltages VU, VV, VW are higher than the reference voltage or the low state in which the terminal voltage is lower than the reference voltage continues is measured, When the high time or low time Tc is equal to or greater than the determination time Tp, it is detected that the induced voltage induced in the stator coils 14U, 14V, 14W intersects the reference voltage, and the rotor position is specified. That is, if the high state where the terminal voltages VU, VV, VW are higher than the reference voltage or the low state where the terminal voltages are lower than the reference voltage does not continue for at least the determination time Tp, the induced voltage induced in the stator coils 14U, 14V, 14W is It does not detect crossing with the reference voltage.

  In such a configuration, when the brushless motor 10 is driven and controlled, a normal induced voltage induced in the stator coils 14U, 14V, and 14W according to the rotor position, and a short time external noise or ringing noise superimposed on the induced voltage. Can be distinguished. For this reason, it is possible to suppress the influence of noise when detecting the rotor position using the induced voltages of the stator coils 14U, 14V, and 14W.

  In the driving device 12 of this embodiment, the determination time Tp for comparing the high time or the low time Tc is changed according to the current duty-on time of the PWM signal. Specifically, a time shorter than the duty on time (for example, 90% thereof) is set according to the duty on time. The determination time Tp is changed according to the power supply voltage (specifically, the reference voltage). Specifically, the time is set shorter as the power supply voltage is smaller.

  In such a configuration, even if the PWM signal has any duty ratio (especially if it has a high duty ratio), the determination time Tp is always set beyond the duty on time. Therefore, it is possible to improve the accuracy of discriminating between the noise and the normal induced voltage, and as a result, it is possible to detect the rotor position while eliminating the noise as much as possible. Further, although the magnitude (width) of noise is proportional to the magnitude of the power supply voltage, in the above configuration, the longer the determination time Tp is set as the power supply voltage is larger, the noise is distinguished from the normal induced voltage. As a result, the rotor position can be detected while eliminating noise as much as possible.

  On the other hand, in this embodiment, in order to detect that the induced voltage induced in the stator coils 14U, 14V, 14W crosses the reference voltage, the output of the comparators 30U, 30V, 30W becomes a high signal. Alternatively, since it is necessary for the state to become a low signal to continue for the determination time Tp, there is a possibility that a delay is caused by the determination time Tp.

  On the other hand, in the present embodiment, after the induced voltage of the stator coils 14U, 14V, 14W intersects the reference voltage, switching between the energized phase and the non-energized phase at the timing when the time corresponding to an electrical angle of 30 ° has elapsed. Is done. That is, after the induced voltage and the reference voltage intersect, drive control is not performed until a time corresponding to an electrical angle of 30 ° elapses, and it is not necessary to switch between the energized phase and the non-energized phase.

  Therefore, in the present embodiment, the control device 40 corrects the detection delay time corresponding to the above-described determination time Tp and executes drive control of the brushless motor 10. Specifically, when it is detected that the induced voltage induced in the stator coils 14U, 14V, and 14W intersects the reference voltage, the terminal is used for the detection before the detected timing (time t1 in FIG. 3). The timing when the voltages VU, VV, and VW first become equal to or higher than the reference voltage (time t2 in FIG. 3) is set later as the reference time necessary for drive control (when the induced voltage crosses the reference voltage). Then, a time corresponding to an electrical angle of 30 ° is calculated from the reference time to switch between the energized phase and the non-energized phase.

  According to such a configuration, the detection that the induced voltage induced in the stator coils 14U, 14V, and 14W intersects the reference voltage is delayed by the determination time Tp from the actual intersecting time point, so It is possible to prevent delay in switching to the energized phase. Therefore, according to the drive device 12 of the brushless motor 10 of the present embodiment, the energized phase and the non-energized phase can be switched at an ideal timing, and the drive control of the brushless motor 10 can be appropriately performed. ing.

  In the above embodiment, the terminal voltage VU, VV, VW is input to the non-inverting input terminals of the comparators 30U, 30V, 30W. 30U, 30V, 30W are the “comparison means” described in the claims, the comparison circuit 46 is the “time determination means” described in the claims, and the main control circuit 48 is the high output timing of the comparison circuit 46. The main control circuit 48 detects that the induced voltage induced in the stator coils 14U, 14V, 14W intersects the reference voltage based on the “induced voltage detecting means” described in the claims. In the “rotor position specifying means” described in the claims, the determination time generation circuit 52 detects the crossing of the reference signal with the reference voltage. Changing the determination time Tp according to the duty ratio of the PWM signal from the generation circuit 54 is the “first determination time changing means” described in the claims, and the determination time generation circuit 52 corresponds to the reference voltage. Changing the determination time Tp is based on the “second determination time changing means” described in the claims, and the main control circuit 48 determines the energization timing to the stator coil 14 of each phase based on the specified rotor position. The control corresponds to the “energization control means” recited in the claims.

  In the above embodiment, the determination time Tp to be used in the comparison circuit 46 is changed according to the duty ratio of the PWM signal. However, the present invention is not limited to this, and the period of the PWM signal is changed. It is good also as changing according to. The determination time Tp is set to, for example, 10% of the time shorter than the period of the PWM signal. In such a configuration, it is always avoided that the determination time Tp is set beyond the period of the PWM signal, regardless of the period of the PWM signal. Therefore, the accuracy of distinguishing noise from the normal induced voltage is avoided. As a result, it is possible to detect the rotor position while eliminating noise as much as possible.

It is a block diagram of the drive device of the brushless motor which is one Example of this invention. It is an operation | movement time chart for performing the rotor position detection in the drive device of the brushless motor of a present Example. It is a characteristic operation time chart in the drive device of the brushless motor of this example. It is a flowchart of an example of the control routine performed in the drive device of the brushless motor of the present embodiment. It is the figure showing the map used when calculating determination time Tp in the drive device of the brushless motor of a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Brushless motor 12 Drive apparatus 14 Stator 16 Inverter circuit 17U Output terminal 30 Comparator 40 Control apparatus 44 Counter 46 Comparison circuit 48 Main control circuit 50 Voltage value monitoring circuit 52 Judgment time generation circuit

Claims (5)

A brushless motor drive device comprising rotor position specifying means for specifying a rotor position based on an induced voltage generated in a stator coil of each phase,
Terminal voltage detection means for detecting the terminal voltage of the stator coil of each phase;
Comparing means for comparing the terminal voltage detected by the terminal voltage detecting means with a reference voltage serving as a reference in specifying the rotor position by the rotor position specifying means;
Time determination means for determining whether or not a state in which the terminal voltage is equal to or higher than the reference voltage continues for a predetermined time as a comparison result of the comparison means;
And the induced voltage detecting means for detecting that when it is determined that the state has continued the predetermined time, the pre-Symbol induced voltage crosses said reference voltage by said time determination means,
First determination time changing means for increasing the predetermined time according to an increase in duty ratio or duty cycle of a pulse width modulation signal for controlling energization to the stator coil of each phase;
A drive device for a brushless motor, comprising:   A brushless motor drive device comprising rotor position specifying means for specifying a rotor position based on an induced voltage generated in a stator coil of each phase,
  Terminal voltage detection means for detecting the terminal voltage of the stator coil of each phase;
  Comparing means for comparing the terminal voltage detected by the terminal voltage detecting means with a reference voltage serving as a reference in specifying the rotor position by the rotor position specifying means;
  Time determination means for determining whether or not a state in which the terminal voltage is equal to or higher than the reference voltage continues for a predetermined time as a comparison result of the comparison means;
  An induced voltage detecting means for detecting that the induced voltage crosses the reference voltage when the time determining means determines that the state has continued for the predetermined time;
  First determination time changing means for setting the predetermined time to a time shorter than a duty on time or a duty cycle in accordance with a duty ratio or a duty cycle of a pulse width modulation signal for controlling energization to a stator coil of each phase When,
  A drive device for a brushless motor, comprising: The first determination time changing means, further wherein the predetermined time before Symbol brushless motor driving device according to claim 1 or 2, wherein the reference voltage is characterized by long response to increases. A brushless motor drive device comprising rotor position specifying means for specifying a rotor position based on an induced voltage generated in a stator coil of each phase,
Terminal voltage detection means for detecting the terminal voltage of the stator coil of each phase;
Comparing means for comparing the terminal voltage detected by the terminal voltage detecting means with a reference voltage serving as a reference in specifying the rotor position by the rotor position specifying means;
Time determination means for determining whether or not a state in which the terminal voltage is equal to or higher than the reference voltage continues for a predetermined time as a comparison result of the comparison means;
And the induced voltage detecting means for detecting that when it is determined that the state has continued the predetermined time, the pre-Symbol induced voltage crosses said reference voltage by said time determination means,
A second determination time changing means for increasing the predetermined time according to an increase in the reference voltage;
A drive device for a brushless motor, comprising: Brushless motor according to any one of claims 1 to 4, characterized in that it comprises a current supply control means for controlling the timing of energization to each phase of the stator coils on the basis of the rotor position specified by the rotor position specifying means Drive device.